Anatomy & Physiology Study Guide: Integumentary, Skeletal, and Articular Systems

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Integumentary System

Major Parts of the Integumentary System

The integumentary system is composed of two primary components that work together to protect the body and maintain homeostasis.

Epidermis: The outermost layer of skin, providing a barrier against environmental hazards.
Dermis: The deeper layer beneath the epidermis, containing connective tissue, blood vessels, nerves, and glands.
Additional info: The subcutaneous layer (hypodermis) is sometimes considered part of the system, providing insulation and cushioning.

Functions of the Integumentary System

The integumentary system serves several vital functions for the body:

Protection: Shields underlying tissues from mechanical damage, pathogens, and harmful substances.
Thermoregulation: Regulates body temperature through sweat production and blood flow.
Sensation: Contains sensory receptors for touch, pain, pressure, and temperature.
Excretion: Removes waste products through sweat.
Vitamin D Synthesis: Initiates the production of vitamin D when exposed to sunlight.
Water Resistance: Prevents excessive water loss and entry.

Homeostasis Example

The integumentary system maintains homeostasis by regulating body temperature. For example, when the body overheats, sweat glands release sweat, which evaporates and cools the skin.

Skin Structure Identification

The skin consists of several layers and structures:

Cutaneous membrane: The skin itself, including epidermis and dermis.
Subcutaneous layer (hypodermis): Fat-rich layer beneath the skin.
Hair follicles, sweat glands, sebaceous glands, sensory receptors, blood vessels: Specialized structures within the dermis and hypodermis.

Layers of the Epidermis

The epidermis is organized into distinct layers, each with specific functions:

Stratum basale (germinativum): Deepest layer, site of cell division.
Stratum spinosum: Provides strength and flexibility.
Stratum granulosum: Cells begin to die and keratinize.
Stratum lucidum: Present only in thick skin (palms, soles).
Stratum corneum: Outermost layer, composed of dead, keratinized cells.

Keratinocytes and Cell Junctions

Keratinocytes are the predominant cell type in the epidermis, producing keratin for strength and waterproofing. They are linked by desmosomes, which provide structural integrity.

Other Epidermal Cells

Melanocytes: Produce melanin pigment for UV protection.
Langerhans cells: Immune defense.
Merkel cells: Sensory receptors for touch.

Thick vs. Thin Skin

Thick skin: Found on palms and soles; contains five layers (including stratum lucidum).
Thin skin: Covers most of the body; contains four layers.

Callus Formation

A callus forms due to repeated friction or pressure, stimulating increased keratinocyte production and thickening of the stratum corneum.

Dermis Structure

Papillary layer: Composed of areolar connective tissue, contains capillaries and sensory neurons.
Reticular layer: Dense irregular connective tissue with collagen and elastic fibers.

Dermal Features

Epidermal ridges: Form fingerprints, improve grip.
Tension lines: Collagen fiber orientation; surgeons cut along these to minimize scarring.
Flexure lines: Skin folds at joints.
Keloid scar: Excessive collagen formation after injury.

Hypodermis

The hypodermis is primarily composed of adipose tissue and areolar connective tissue, providing insulation and energy storage.

Exocrine Glands of the Skin

Sudoriferous (sweat) glands: Thermoregulation and excretion.
Sebaceous (oil) glands: Lubricate skin and hair.
Ceruminous glands: Produce earwax.

Skin Damage and Melanin

Causes of skin damage: UV radiation, chemicals, physical trauma, infections.
Melanin production: Melanocytes synthesize melanin from tyrosine, which is transferred to keratinocytes.
Melanin and Vitamin D: Melanin absorbs UV light, reducing vitamin D synthesis.
Melanocyte number: The number of melanocytes is similar across skin colors; variation is due to melanin production.

Skin Coloration Terms

Erythema: Redness due to increased blood flow.
Pallor: Paleness from reduced blood flow.
Cyanosis: Bluish color from low oxygen.
Jaundice: Yellowing from bilirubin accumulation.

ABCDE of Skin Cancer Determination

A: Asymmetry
B: Border irregularity
C: Color variation
D: Diameter (>6mm)
E: Evolving (changes over time)

Main Types of Skin Cancer

Basal cell carcinoma: Originates in basal cells; slow-growing.
Squamous cell carcinoma: Arises from squamous cells; may metastasize.
Melanoma: Develops from melanocytes; highly malignant.

Skin Disorders

Jaundice: Liver dysfunction.
Pituitary tumor: Hormonal imbalance affecting pigmentation.
Addison's disease: Adrenal insufficiency causing bronzing.
Vitiligo: Loss of melanocytes, resulting in depigmented patches.

Burns and Rule of Nines

1st degree: Epidermal damage only.
2nd degree: Epidermis and part of dermis.
3rd degree: Full thickness, including hypodermis.

The rule of nines estimates burn area as a percentage of body surface.

Tissue Repair Steps

Inflammation
Organization (formation of granulation tissue)
Regeneration
Fibrosis (scar formation)

Skeletal System

Cartilage

Cartilage is a flexible connective tissue found in joints, ear, nose, and respiratory tract.

Avascular cartilage: Hyaline cartilage lacks blood vessels.
Cartilage cells: Chondroblasts (produce matrix), chondrocytes (maintain matrix).
Function: Provides support, flexibility, and reduces friction.

Bone Classification by Shape

Long bones: Femur, humerus.
Short bones: Carpals, tarsals.
Flat bones: Skull, ribs.
Irregular bones: Vertebrae, pelvis.

Functions of Bone

Support
Protection
Movement
Mineral storage (calcium, phosphate)
Blood cell production (hematopoiesis)

Bone Cells

Osteoblasts: Build bone matrix.
Osteocytes: Mature bone cells, maintain matrix.
Osteoclasts: Break down bone matrix.

Long Bone Structure

Diaphysis: Shaft
Epiphysis: Ends
Medullary cavity: Contains bone marrow
Periosteum: Outer covering
Endosteum: Lining of medullary cavity

Compact vs. Spongy Bone

Compact bone: Dense, forms outer layer, provides strength.
Spongy bone: Porous, contains trabeculae, found in epiphyses.

Bone Marrow

Red bone marrow: Hematopoiesis (blood cell formation).
Yellow bone marrow: Fat storage.

Bone Growth and Ossification

Interstitial growth: Growth in length.
Appositional growth: Growth in thickness.

Endochondral ossification is the process by which cartilage is replaced by bone, primarily in long bones.

Intramembranous ossification forms flat bones directly from mesenchymal tissue.

Role of Osteoclasts and Osteoblasts

Osteoclasts: Resorb bone during remodeling and growth.
Osteoblasts: Deposit new bone matrix.

Calcification

Calcification is the deposition of calcium salts within tissue, essential for bone hardness.

Vitamin D3 and Calcium Regulation

Vitamin D3: Facilitates calcium absorption in the intestine.
Calcium regulation: Parathyroid hormone (PTH) increases blood calcium; calcitonin lowers it.

Types of Fractures

Transverse
Oblique
Spiral
Comminuted
Greenstick
Compression

Abnormal Spinal Curvatures

Scoliosis
Kyphosis
Lordosis

Bone Disorders

Osteopenia: Reduced bone mass.
Osteoporosis: Severe bone loss, increased fracture risk.
Bone cancer: Malignant growth in bone tissue.

Articular System (Joints)

Joint Classification Table

Structural Classification	Characteristics	Categories	Functional Classification
Fibrous	Dense connective tissue, no cavity	Sutures, syndesmoses, gomphoses	Synarthrosis or amphiarthrosis
Cartilaginous	Cartilage joins bones, no cavity	Synchondroses, symphyses	Synarthrosis or amphiarthrosis
Synovial	Joint cavity, synovial fluid	Plane, hinge, pivot, condyloid, saddle, ball-and-socket	Diarthrosis

Functions of Joints

Enable movement
Provide stability
Allow growth

Joint Terminology

Synarthrosis: Immovable joint
Amphiarthrosis: Slightly movable joint
Diarthrosis: Freely movable joint

Fibrous Joint Locations

Sutures: Skull
Syndesmoses: Between radius and ulna
Gomphoses: Teeth in sockets

Synovial Fluid and Joint Axes

Synovial fluid: Lubricates and nourishes joint
Uni-axial: Movement in one plane (hinge, pivot)
Bi-axial: Movement in two planes (condyloid, saddle)
Multi-axial: Movement in multiple planes (ball-and-socket)

Synovial Joint Types and Locations

Plane: Intercarpal joints (uni-axial)
Hinge: Elbow, knee (uni-axial)
Pivot: Atlantoaxial joint (uni-axial)
Condyloid: Wrist (bi-axial)
Saddle: Thumb (bi-axial)
Ball-and-socket: Shoulder, hip (multi-axial)

Dislocation Types

Anterior dislocation: Bone displaced forward
Posterior dislocation: Bone displaced backward

Connective Tissue Structures

Ligament: Connects bone to bone
Tendon: Connects muscle to bone
Bursa: Fluid-filled sac reducing friction

Aging Effects on Joints

Decreased flexibility
Cartilage degeneration
Increased risk of arthritis

Joint Disorders

Arthritis: Inflammation of joints
Lyme Disease: Infection causing joint pain
Gout: Uric acid crystal deposition
Bunion: Deformity of big toe joint
Chondromalacia patellae: Softening of knee cartilage

Joint Movements

Flexion vs. Extension: Flexion decreases angle; extension increases angle.
Abduction vs. Adduction: Abduction moves limb away from midline; adduction moves it toward midline.
Elevation vs. Depression: Elevation raises a body part; depression lowers it.

Body Part Movements

Neck: Flexion, extension, rotation
Body: Flexion, extension
Elbow: Flexion, extension
Forearm: Pronation, supination
Wrist: Flexion, extension, abduction, adduction
Fingers: Flexion, extension, abduction, adduction
Arm: Flexion, extension, abduction, adduction, rotation
Hip: Flexion, extension, abduction, adduction, rotation
Legs: Flexion, extension
Knee: Flexion, extension
Ankle: Dorsiflexion, plantarflexion
Toes: Flexion, extension